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A006248 Number of primitive sorting networks on n elements. Number of projective pseudo order types: simple arrangements of pseudo-lines.
(Formerly M3428)
1, 1, 1, 1, 1, 4, 11, 135, 4382, 312356, 41848591 (list; graph; refs; listen; history; text; internal format)



J. Bokowski, personal communication.

J. Ferte, V. Pilaud and M. Pocchiola, On the number of simple arrangements of five double pseudolines. Discrete Comput. Geom. 45 (2011), 279-302.

Lukas Finschi, A Graph Theoretical Approach for Reconstruction and Generation of Oriented Matroids, A dissertation submitted to the Swiss Federal Institute of Technology, Zurich for the degree of Doctor of Mathematics, 2001.

Fukuda, Komei; Miyata, Hiroyuki; Moriyama, Sonoko. Complete Enumeration of Small Realizable Oriented Matroids. Discrete Comput. Geom. 49 (2013), no. 2, 359--381. MR3017917. - From N. J. A. Sloane, Feb 16 2013

J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102.

D. E. Knuth, Axioms and Hulls, Lect. Notes Comp. Sci., Vol. 606.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


Table of n, a(n) for n=1..11.

J. Bokowski & N. J. A. Sloane, Emails, June 1994

L. Finschi, Homepage of Oriented Matroids

L. Finschi and K. Fukuda, Complete combinatorial generation of small point set configurations and hyperplane arrangements, pp. 97-100 in Abstracts 13th Canadian Conference on Computational Geometry (CCCG '01), Waterloo, Aug. 13-15, 2001.

Index entries for sequences related to sorting


Cf. A006245, A006246, A018242, A063666. A diagonal of A063851.

Sequence in context: A167418 A055979 A018242 * A119571 A089920 A303881

Adjacent sequences:  A006245 A006246 A006247 * A006249 A006250 A006251




N. J. A. Sloane


a(11) from Franz Aurenhammer (auren(AT)igi.tu-graz.ac.at), Feb 05 2002



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Last modified July 18 01:14 EDT 2019. Contains 325110 sequences. (Running on oeis4.)